2025 American Academy of Neurology Abstract Website

Objective:

We aim to present a case series of Eastern Equine Encephalitis (EEE) focusing on the clinical and radiographic features as well management strategies employed to treat this rare neuroinvasive arbovirus.

Background:

EEE is a rare but severe neuroinvasive arboviral disease with significant morbidity and mortality. Early diagnosis and intervention are crucial to improving patient outcomes.

Design/Methods:

A single center retrospective descriptive cases series of five patients with EEE is presented. the CARE guidelines for case reports/series was followed. The clinical features including age, gender, presenting symptoms, as well as treatment strategies and outcomes are reported. Additionally, radiographic features including magnetic resonance imaging (MRI) findings are described.

Results:

We report a 20% mortality rate. The average hospital stay among survivors was 10 days. 60% required mechanical ventilation. A variety of neurological symptoms, including altered mental status, seizures, and focal neurological deficits. Diagnosis of EEE was confirmed in four patients by detection of EEE-specific IgM antibodies in cerebrospinal fluid (CSF), one patient with negative CSF EEE IgM/IgG however positive EEG IgM in serum. CSF studies also showed elevated protein, red blood cells, normal or high glucose, and elevated white blood cells with lymphocytic or neutrophil predominance. MRI showed T₂ hyperintensities in the basal ganglia, thalamus, and cortical regions. Three cases showed encapsulation as evidence by a hyperintense ring around the basal ganglia or thalamus. EEG findings ranged from normal, focal irritability and spikes to nonconvulsive status epilepticus. Clinical and/or electrographic evidence of seizure was seen in four cases. Two patients were treated with high-dose intravenous methylprednisolone and one with intravenous immunoglobulin (IVIG) to modulate the immune response. One patient received IV dexamethasone in low dose (10 mg/day).

Conclusions:

This case series underscores the importance of maintaining a high clinical suspicion of EEE in patients with acute neurological symptoms. Early use of high-dose steroids may improve outcomes.